DEFINITION MODULE Processes;
(*
  Module:	Processes
  From:		"Programming in Modula-2", 3rd, corrected edition, by N. Wirth
  Version:	$Header$
*)
(*
  As discussed in "Unfair Process Scheduling in Modula-2", by
  D. Hemmendinger, SIGplan Notices Volume 23 nr 3, march 1988,
  the scheduler in this module is unfair, in that in some circumstances
  ready-to-run processes never get a turn.
*)

	TYPE SIGNAL;

	PROCEDURE StartProcess(P: PROC; n: CARDINAL);
	(* Start a concurrent process with program "P" and workspace of
	   size "n"
	*)

	PROCEDURE SEND(VAR s: SIGNAL);
	(* One process waiting for "s" is resumed
	*)

	PROCEDURE WAIT(VAR s: SIGNAL);
	(* Wait for some other process to send "s"
	*)

	PROCEDURE Awaited(s: SIGNAL): BOOLEAN;
	(* Return TRUE if at least one process is waiting for sinal "s".
	*)

	PROCEDURE Init(VAR s: SIGNAL);
	(* Compulsory initialization
	*)
END Processes.